How to Buy Next Generation Sequencing Technology
11 May 2017

Introduction

DNA sequencing has advanced significantly since the launch of the Human Genome Project in 1990. A human genome can now be sequenced in under 10 days for less than $1,000, and soon will be sequenced routinely within a day. This remarkable process is due to significant advances in DNA sequencing, from Sanger sequencing – which has been dominant for almost 30 years – to next generation sequencing (NGS, also termed massively parallel sequencing).

Sanger sequencing, which is often considered first generation sequencing technology, utilizes capillary electrophoresis to separate fragments of DNA by size and then sequences them by detecting the final fluorescent base on each fragment. This widely adopted technology is still extremely important today, but has always been hampered by inherent limitations in throughput, scalability, speed and resolution.

The limitations associated with Sanger sequencing have catalyzed the development of NGS technologies, which can inexpensively and quickly produce large volumes of sequence data. NGS enables rapid sequencing of large stretches of DNA base pairs spanning entire genomes, with some instruments capable of producing hundreds of gigabases of data in a single sequencing run. The read length – the actual number of continuous sequenced bases – is much shorter in NGS than that attained by Sanger sequencing, and at present NGS only provides 50-500 continuous base pair reads. Short reads represent the major limitation currently associated with NGS.

NGS technology is evolving at an unprecedented speed. Scientists can now routinely examine a single genome a large number of times, observe individual changes, study population variations, study the microbiome and metagenomics, differentiate cancer genomes from healthy genomes, study the epigenome, and investigate the possibility of personalized medicine, among other applications.

NGS Technology & Sequencers

There are several main suppliers of next generation sequencing instruments and they all share the same fundamental sequencing process, but with varying technologies. Regardless of their method of arrival, next generation sequencers rely on the generation of representative, unbiased sources of nucleic acid templates from the complex genomes being interrogated. Clonally amplified DNA templates, or single DNA molecules, are sequenced in a massively parallel fashion in a flow cell. The sequencing is conducted in either a stepwise iterative process or in a continuous real-time manner. In this way, the instruments allow for the sequencing of up to billions of individual DNA templates in a single reaction.

Ion Torrent™ Technology

Thermo Fisher Scientific’s (formerly Life Technologies) Ion Torrent™ Technology directly translates chemically encoded information (A, C, G, T) into digital information (0, 1) on a semiconductor chip, similar to the one you might find in your digital camera. The Ion Personal Genome Machine™ (PGM™) sequencer essentially acts as the world’s smallest solid-state pH meter to determine DNA sequences. The DNA is fragmented, attached to beads and deposited in millions of wells across the surface of the chip. The wells are then sequentially flooded with one nucleotide after another. If a nucleotide is incorporated into the strand of bead-bound DNA, a hydrogen ion is given off, a chemical change is measured by an ion sensor beneath the well, and a base is called. This process takes place in millions of wells simultaneously, enabling sequencin